In vivo Dopamine Pre-Synaptic Receptors and Antioxidant Activities in Patients with Alzheimer’s Disease, Dementia with Lewy Bodies and in Controls

Abstract

The degeneration of dopaminergic cells in dementia with Lewy bodies (DLB) may provide an important source of additional free radical generation. As a result, the oxidative stress status in DLB could be significantly enhanced. Subsequently, the levels of endogenous antioxidants, which are an indirect measure of free radical activities, may be different in DLB patients when compared with Alzheimer’s disease (AD) patients and controls. In this preliminary study, we measured the activities of superoxide dismutase (SOD), catalase (CAT), glutathione (GLU) and total antioxidant capacity in the blood of DLB, AD and control subjects. The state of nigrostriatal dopaminergic system was also assessed in vivo by using a radioactive ligand with an affinity for the dopamine pre-synaptic receptors and by imaging with single-photon emission tomography. Data obtained showed a decrease in dopamine pre-synaptic receptors in all the brain regions of DLB patients. The levels of SOD did not differ significantly between DLB, AD and control subjects. However, GLU levels were significantly higher in the DLB patients when compared with AD patients (p < 0.05) and controls (p < 0.01). CAT blood levels were also higher in DLB when compared with AD, but this did not reach statistical significance. The results suggest that a different oxidative stress state may exist in DLB. This may occur due to increased free radical production from the degeneration of dopaminergic cells and auto-oxidation of dopamine, the availability of which may be maintained in early-stage DLB disease as a result of the compensatory increase in its turnover from the remaining dopaminergic cells.